This invention relates to a howling detection and prevention circuit and a loudspeaker system employing this circuit.
In radiating an acoustic power using a microphone and a loudspeaker, a loud sound produced by the loudspeker is sometimes accompanied by howling. For preventing howling, it is conceivable to increase entire gain of radiation of an acoustic power in which howling is produced by restraining the entire gain of radiation of acoustic power to a level which is below a level at which howling is produced or reduce the gain of a frequency region in which howling starts to take place. In the past, for preventing howling, a user manipulates a volume control while confirming presence or absence of howling to set the entire gain of radiation of acoustic power to a level at which howling is not produced or sets the entire gain after decreasing the gain of a particular frequency region by using a graphic equalizer or a notch filter. Adjustment of the gain is made relying upon the user's hearing. Once howling has occurred, the user usually hurries to the loudspeaker system and stops howling by lowering the volume level. In such a case, it takes time before howling stops and the user cannot avoid unpleasantness caused by howling during this time.
Thus, manual adjustment of the gain for preventing occurrence of howling in the prior art loudspeaker system has caused the problems of lack in accuracy and stability, requirement for the troublesome adjustment and requirement for time for adjustment.
It is, therefore, an object of the invention to provide a howling detection and prevention circuit capable of automatically detecting and preventing howling and a loudspeaker system employing the same circuit.